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L. F. Delgado-Aparicio, D. Stutman, K. Tritz, and M. Finkenthal The Plasma Spectroscopy Group

Tangential multi-color “optical” soft X-ray array for fast electron temperature and transport measurements. L. F. Delgado-Aparicio, D. Stutman, K. Tritz, and M. Finkenthal The Plasma Spectroscopy Group The Johns Hopkins University R. Bell, D. Johnson, R. Kaita, B. LeBlanc and L. Roquemore

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L. F. Delgado-Aparicio, D. Stutman, K. Tritz, and M. Finkenthal The Plasma Spectroscopy Group

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  1. Tangential multi-color “optical” soft X-ray array for fast electron temperature and transport measurements L. F. Delgado-Aparicio, D. Stutman, K. Tritz, and M. Finkenthal The Plasma Spectroscopy Group The Johns Hopkins University R. Bell, D. Johnson, R. Kaita, B. LeBlanc and L. Roquemore Princeton Plasma Physics Laboratory Princeton Plasma Physics Laboratory NSTX Results/Research Forum December, 12-17, 2005 Princeton, New Jersey, USA

  2. Principles of the “optical” soft x-ray (OSXR) array Conversion to visible light OSXR array head tested on CDX-U & NSTX spherical tokamaks (2004) vacuum vacuum To discrete channels and light (PMT and/or APDs) amplifiers It’s a system that uses a fast (1 s) and efficient scintillator (CsI:Tl) in order to convert soft x-ray photons (0.1<Eph<10 keV) to visible green light(550 nm).

  3. Motivation • Fast ( 100 s) Te measurements. (ECE-like diagnostic for STs and Tokamaks)  Perturbative electron heat and particle transport (ELMs, pellets, gas-puff and/or SGI).  MHD related Te perturbations (ELMs, MHD-modes, RWMs, FISHBONES/EPMs). • Perturbative impurity transport. (Gas puff (Ne), Impurity pellets (C, B) and/or SGI) Our previous work with the USXR and the 1-color OSXR systems have shown that the measurements proposed are feasible. • Explore the possibilities of the proposed diagnostic in poloidal configuration.  Viewing the same plasma volumes at three energy ranges.  Higher SNR in comparison to diode-based arrays.

  4. How to design a diagnostic to measure Te(r,t)? Tangential multi-color (3) optical soft x-ray (tMC-OSXR) array Multi-color technique (two-foil method): • The Te measurement is obtained by rationing the localizedradiation intensities from two energy ranges, rather than from an absolute intensity measurement, as is in the case of a single color instrument. • This design approach naturally eliminates a number of factors that degrade the accuracy of the conventional single color SXR diagnostics for Te measurements. • Absolute value of the Te(r) by minimization techniques! • Feedback ne(r,t)nZ(r,t)

  5. Details of the optical head 8” CF flange Soller slits Baffles 8” 2 cm 2 cm Filter holder 4” Baffles Filter holders (10, 100 and 300 mm) 8” CF flange with FOW FOC NSTX tangential “optical” soft x-ray (tOSXR) array Rtg15~84 cm Rtg00~146.5 cm • Components • Baffles + filters • Soller slits • Scintilator + FOW • Fiber optics • PMTs + shield • Amps • DAQs

  6. SNR10 um ~ 247 SNR100 um ~558 SNR300 um ~ 953 150 ms SNR300/10 ~ 196 SNR100/10 ~ 171 Te0 from tangential line-integrated multi-color ratio Time history of soft X-ray signals NSTX shot # 117951 (RS L-mode) Ip RF NBI 150 ms Sn Da Sn What happen with Sn & Te for t  [0.2,0.35] ?

  7. t2 t1 t1 1.97 1.6 60 eV 130 eV 1.54 1.84 t2 keV “First cut” Te(r,t)tOSXR space-time profile “First cut” Te(r,t)tOSXR space-time profile 2.2 2.2 keV keV 1.3 1.3 Te(r,t) and neutron rates (Sn) crashes

  8. 1.97 1.6 60 eV 1.54 130 eV 1.84 5 ms 5 ms Fishbone Fishbone Te(r) drops: what is preventing the Te0 from peaking? 1 2

  9. MHD fishbones affect background plasma during Dtfish<tsd Observations • Each fishbone burst affect the Te distribution (Te<0) only during the phase of largest amplitude of the MHD oscillation, that is ~ 2-3 ms (Dtfish<tsd) . • The magnitude of the central Te0 is generally correlated with the amplitude of the individual fishbone. • The USXR array identifies fishbones as a reconnection-sawtooth-like processeses (but in a slower time-scale in accordance with tOSXR array). • Fishbones can also affect impurity density profiles, avoiding their central peaking. •  ne measured by UCLA reflectometer •  q0 after the fishbones have disappeared n=1 Fishbones (5 kHz < f < 30 kHz) 2.2 keV 2-4 ms 2-4 ms 1.3  Fishbones in NSTX can lead to a redistribution of Te and nZ similar in form to a sawteeth, but with the plasma parameter variation occurring on a significantly longer time-scale (Dtfish<tsd). q0~0.4 q0~0.7 [1] M. F. F. Nave, et al., Fishbone activity in JET, NF, 31, 697, (1991). [2] T. Kass, et al., The Fishbone instability in ASDEX Upgrade, NF, 38, 807, (1998). [3] S. Günter, et al., The influence of Fishbones in the background plasma, NF, 39, 1535, (1999).

  10. Dt1 Da 1 0.5 0 Type I ELMs study (see also K. Tritz presentation) • Normalized contour plots of tangentially-line-integrated soft x-ray signals, filtered with Be foils with thicknesses of 10, 100 and 300 m, respectively. • Shown here is the effect on the soft x-ray intensity of an edge-localized-mode (ELM) occurring at  327 ms 5 ms NSTX shot # 117903 Dt2 Dt1

  11. 850 eV 50 eV Type I ELM Te(r,t) profiles: Dt1 NSTX shot # 117903, t[0.3,0.35] 5 ms 5 ms inboard core ELM edge

  12. NSTX shot # 117903, t[0.35,0.4] (Be10/Be300) Type I ELM SXR and Te(r,t) profiles: Dt2 inboard 1050 eV core 6 ms 50 eV edge

  13. Future: re-entrant “multi-color” OSXR system? OSXR array head tested on NSTX NSTX (07) & NCSX It’s a system based on the OSXR concept with an optimized plasma access and the capability of recording MHD phenomena from the core to the periphery SIMULTANEOUSLY!

  14. Conclusions • We have designed, build, installed and tested the prototype version of a tangential multi-color optical SXR array for fast electron temperature measurements. • Line integrated signals enabled the measurement of fast electron temperature profiles in good agreement with the (slow) Thomson Scattering measurements. • The tosxr array can work in a variety of plasma scenarios (L-mode & H-mode). • However in the cases of strong inhomogeneities in the local plasma characteristics the limitation of the use of line integrated signals become apparent. Further work • Perform the Abel inversions! • Modify the filter holder to enable photometric calibration in absence of foils. • Use 500 mm Be foil for increase contrast. • Use transimpedance amplifiers (bandwidth: DC-50 kHz) module behind PMT. • Rotate the tOSXR for better plasma access.

  15. Acknowledgments • The Johns Hopkins University: Gaib Morris, Scott Spangler, Steve Patterson, Russ Pelton and Joe Ondorff. • Princeton Plasma Physics Laboratory: Mike Bell, Bill Blanchard, Thomas Czeizinger, John Desandro, Russ Feder, Jerry Gething, Scott Gifford, James Kukon, Doug Labrie, Steve Langish, Jim Taylor, Sylvester Vinson, Doug Voorhes and Joe Winston (NSTX). • This work was supported by The Department of Energy (DOE) grant No. DE-FG02-86ER52314ATDOE

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